ES2767530T3 - Solar cell and its production method - Google Patents

Abstract

Solar cell (110) comprising: a semiconductor substrate (113) of a first type of conductivity in which one of the main surfaces is a light-receiving surface, the other main surface is a rear side, and the rear side of the semiconductor substrate has a region of the first type of conductivity and a region of a second type of conductivity, a type of conductivity being opposite to the first type of conductivity; a first finger electrode including: a first contact portion (126) attached to the region (120) of the first type of conductivity; and a first current collector (135), at least a part of the first current collector being formed in the first contact part; a second finger electrode including: a second contact portion (127) attached to the region (121) of the second type of conductivity; and a second current collector (136), at least a part of the second current collector being formed in the second contact part; a first connecting rod electrode (137) being in electrical contact with the first current collector; a second connecting rod electrode (138) being in electrical contact with the second current collector; and an insulating film (124, 125) disposed at least over the entire area just below the first connecting rod electrode and the second connecting rod electrode; where the electrical contact between the first current collector (135) and the first connecting rod electrode (137), as well as the electrical contact between the second current collector (136) and the second connecting rod electrode (138) they are made on the insulating film; and the first contact part (126) and the second contact part (127) are each in the form of a solid line at least just below the insulating film.

Description

DESCRIPTION

Solar cell and its production method

Technical field

The present invention relates to a solar cell and a production method thereof.

Background of the Art

An earlier rear surface electrode type solar cell is shown schematically in Figure 14 as a cross sectional view. The back surface electrode type solar cell 210 produced by a prior art will be described with reference to FIG. 14. On the light receiving surface side of a N type silicon substrate 213, a rough shape 214 and a FSF layer (front surface field) 215, which is an N-type diffusion layer. In rough form 214, a dielectric passivation layer (a passivation layer of surface) 217 containing silicon dioxide and an anti-reflective film 216 containing silicon nitride.

On the back side of the N 213 type silicon substrate, N-type doped diffusion layers are alternately formed with N 220 type and P type doped diffusion layers with type P 221. In addition, on the back side of the N 213 type silicon substrate , an oxide layer is formed (the first subsequent passivation film) 219. In the N-type diffusion layer 220, a N-type 211 contact electrode is formed; and in the diffusion layer type P 221, a contact electrode type P 212 is formed. These contact electrodes, which are directly attached to the substrate itself, can also function as finger electrodes to collect current.

Fig. 15 is a top view schematically showing the appearance of the posterior side of the posterior surface electrode type solar anterior cell. As shown in Figure 15, the back surface electrode type solar cell is provided with a pair of connecting rod electrodes (one connecting rod electrode type N 222, one connecting rod electrode type P 223) at the edge of the substrate to collect current from the finger electrodes (the N 211 type contact electrode, or the P 212 type contact electrode). Although the electrodes closest to the periphery of the substrate are represented as N-type contact electrodes in Figure 15, they can be P-type contact electrodes or metal electrodes of different types, each being P-type and N-type.

To improve the efficiency of the back surface electrode type solar cell, the full expansion of the P-type diffusion layer, which is a power generation layer, can be expected to increase the short-circuit current. Accordingly, it is desirable to widely form the region of the P-type diffusion layer, such as the area ratio of the P-type diffusion layer and the N-type diffusion layer in a range of 80:20 to 90:10. When the contact area between the substrate and the contact electrodes (hereinafter, also called the contact area) is decreased as much as possible, and the passivation regions are enlarged, an increase in circuit voltage can be expected. open. Therefore, it is desirable to design the contact region as small as possible by making the contact electrodes with thin line or dot shapes.

Patent Document 1 discloses a back surface electrode type solar cell in which the contact area of the electrodes and the substrate is suppressed as little as possible, and the passivation regions are expanded in three stages of formation of contact electrodes, covering the different part of the contact electrodes with an insulating film, and forming a wiring electrode.

Fig. 17 is a top view schematically showing the appearance of the rear side of the above rear surface electrode type solar cell disclosed in patent document 1. In the solar cell of patent document 1, without However, only one pair of connecting rod electrodes (one connecting rod electrode type N 222, one connecting rod electrode type P 223) are formed at the periphery of the substrate (see Figure 17). In this arrangement, the finger electrodes are long, and consequently the wiring resistance becomes extremely large, causing a fill factor to decrease. This wiring resistance becomes greater in proportion to the length of the wiring. It is considered that this can be solved by designing the wiring electrodes (finger electrodes) so that they have an enlarged cross section or so that the finger has a shortened length.

List of cited documents

Patent bibliography

Patent Document 1: Japanese Patent No. 5317209

DE 10 2007 003682 A1 relates to a solar cell comprising a semiconductor substrate and electrodes.

Summary of the invention

Technical problem

As described above, it has been requested that a solar cell be able to have an enlarged cross section of the finger electrodes and a shortened length of the finger electrodes while having a reduced contact area. Accordingly, it has been investigated to make the electrode structure of a back surface electrode type solar cell a three-dimensional structure, etc. The anterior three-dimensional structure formed in the electrode structure, however, tends to decrease the resistance in parallel.

The present invention was accomplished in view of the problems described above. It is an object of the present invention to provide a solar cell with a wide passivation region, low wiring resistance, high parallel resistance and high conversion efficiency; and providing a method of producing a solar cell that can produce such a solar cell at low cost.

Solution to the problem

To solve the problems described above, the present invention provides a solar cell (110) comprising:

a semiconductor substrate (113) of a first type of conductivity in which one of the main surfaces is a light receiving surface, the other main surface is a back side, and the back side of the semiconductor substrate has a region of the first type of conductivity and a region of a second type of conductivity, a type of conductivity being opposite to the first type of conductivity;

including a first finger electrode: a first contact part (126) attached to the region (120) of the first type of conductivity; and a first current collector (135), at least a part of the first current collector being formed on the first contact part;

including a second finger electrode: a second contact part (127) attached to the region (121) of the second type of conductivity; and a second current collector (136), at least a part of the second current collector being formed on the second contact part;

a first connecting rod electrode (137) being in electrical contact with the first current collector;

a second connecting rod electrode (138) being in electrical contact with the second current collector; and

an insulating film (124, 125) disposed at least in the complete area just below the first connection rod electrode and the second connection rod electrode;

where the electrical contact between the first current collector (135) and the first connection bar electrode (137), as well as the electrical contact between the second current collector (136) and the second connection bar electrode (138) they are made on the insulating film; and

the first contact part (126) and the second contact part (127) are each in a continuous line shape at least just below the insulating film.

In such a solar cell, it is possible to increase the number of the connecting rod electrodes, shorten the length of the finger electrodes and collect current from the finger electrodes on both sides of the connecting rod electrodes by installing a film insulating and forming a three-dimensional structure of connecting rod electrodes and finger electrodes. As a result, it is possible to decrease the wiring resistance and increase the fill factor. In addition to the insulating film, whereby the connecting rod electrodes and finger electrodes for different types of conductivity will not be in contact with each other, the connecting rod electrodes are not in contact with the substrate directly, which makes make the solar cell difficult to drift. The region that has the connecting rod electrodes formed is flat, and it is difficult to generate bleeding thereby in the formation of the connecting rod electrodes. As a result, the solar cell can have high resistance in parallel. Furthermore, the contact parts are each in a continuous line form just below the insulating film and therefore it is possible to form a three-dimensional structure of connecting rod electrodes and finger electrodes without increasing the number of stages in production .

It should be noted that the shunt referred to herein means a decrease in parallel resistance. This is likely caused by a connection between the P-type finger electrode and the N-type finger electrode (i.e. short circuit) through the connecting rod electrode or diffusion layer that has the same type of conductivity (the layer type N diffusion layer or type P diffusion layer). The term "derive" means to form such a state.

As described above, even by reducing the contact part to enlarge the passivation regions as much as possible, the presence of the current collector makes it possible to enlarge the cross section of the finger electrodes and decrease the wiring resistance. Such a solar cell can be a low cost solar cell with low wiring resistance and high conversion efficiency.

On the other hand, the connection bar electrode refers to a current collecting electrode that is in electrical connection with a current collector of a finger electrode. The connecting rod electrode is generally formed in a position that almost intersects the finger electrode at right angles.

It is preferable that the first connecting rod electrode and the second connecting rod electrode are each in a continuous line form, and the insulating film is in a continuous line form.

Such a solar cell can make a module more reliable.

It is also preferable that the total number of the first connecting rod electrode and the second connecting rod electrode is 4 or more and 10 or less.

Such a solar cell can further decrease the wiring resistance of the finger electrode without increasing the thickness of the finger electrode. For example, compared to a case where the total number of connecting rod electrodes is 2, the wiring resistance can be reduced to one sixth when the total number is 6, and to one tenth when the total number is 10.

It is also preferable that the insulating film is composed of a material containing one or more resins selected from the group consisting of silicone resins, polyimide resins, polyamide-imide resins, phenolic fluororesins, melamine resins, urea resins, polyurethanes , epoxy resins, acrylic resins, polyester resins and poval resins.

Insulating films made of such material have excellent thermal resistivity. Therefore, these insulating films are preferable when the heat treatment is carried out in the formation of an electrode.

It is also preferable that the insulating film has a thickness of from 1 to 60 | im.

In such a solar cell, the insulation property can be further improved. It is also possible to produce a desired solar cell at lower cost since the insulating film does not form excessively.

It is also preferable that the first current collector, the second current collector, the first connection bar electrode and the second connection bar electrode are each composed of a material containing one or more kinds of conductive materials selected from the group consisting of Ag, Cu, Au, Al, Zn, In, Sn, Bi and Pb, and one or more classes of resins selected from the group consisting of epoxy resins, acrylic resins, polyester resins, phenolic resins and silicone resins .

When the solar cell is composed of such an electrode material, this electrode material does not directly bond to a semiconductor substrate such as a heating silicon substrate to form an electrode, and therefore an increase in area can be suppressed contact.

The present invention also provides a method for the production of a solar cell that includes a semiconductor substrate of a first type of conductivity in which one of the main surfaces of the semiconductor substrate is a light receiving surface, the other main surface is a back side and back side of the semiconductor substrate has a region of the first type of conductivity and a region of a second type of conductivity, a type of conductivity being opposite to the first type of conductivity; comprising the stages of:

forming the region of the first type of conductivity and the region of the second type of conductivity on the back side;

forming a first contact part attached to the region of the first type of conductivity and a second contact part attached to the region of the second type of conductivity such that each of them has a continuous line shape in at least a part of the same;

forming an insulating film covering the top and the side of the part having a continuous line shape at the first contact part and the second contact part;

forming a first connection bar electrode and a second connection bar electrode only on the insulating film;

forming a first current collector that is in electrical contact with the first connecting rod electrode in the first contact part;

and forming a second current collector that is in electrical contact with the second connecting rod electrode on the second contact part.

Such a method for producing a solar cell can produce a back surface electrode type solar cell with a wide passivation region, low wiring resistance, high parallel resistance and high conversion efficiency at low cost and with high productivity .

It should be noted that the contact part is defined as an electrode that is in contact with the semiconductor substrate, in particular the region of the first type of conductivity and the region of the second type of conductivity in this description. The current collector is defined as an electrode connecting the connecting rod electrode and the contact part. The current collector and the contact part are generically called finger electrode. The current collector can also be referred to as "part of line".

It is preferable that the stage for forming a first connection bar electrode and a second connection bar electrode and the stage for forming a first current collector and a second current collector are performed simultaneously.

This can further reduce the number of stages and can produce a solar cell with higher conversion efficiency at lower cost.

Advantageous effects of the invention

In the inventive solar cell, it is possible to increase the number of connecting rod electrodes, shorten the length of the finger electrodes, and collect current from the finger electrodes on both sides of the connecting rod electrodes by installing insulating films and the formation of a three-dimensional structure of connecting rod electrodes and finger electrodes. As a result, it is possible to decrease the wiring resistance and increase the fill factor. Furthermore, it is possible to increase the cross section of the finger electrode to decrease the wiring resistance while decreasing the contact area by forming the current collectors on the contact part, and thus improve the open circuit voltage. Also, since the connecting rod electrodes are not in contact with the substrate directly, the solar cell will not bypass. Furthermore, it is possible to suppress bleeding in the formation of the connecting rod electrodes by flattening the area to form the connecting rod electrode, thereby improving performance. Furthermore, the inventive method of producing a solar cell can produce such a solar cell without increasing production steps.

Brief description of the drawings

Figure 1 is a top schematic view showing an example of the inventive solar cell;

Fig. 2 is an enlarged view showing an enlarged part of the inventive solar cell;

Figure 3 is a schematic cross-sectional view showing an enlarged part of the inventive solar cell; Figure 4 is a schematic cross sectional view showing an enlarged part of the inventive solar cell; Figure 5 is a schematic cross-sectional view showing an enlarged part of the inventive solar cell; Figure 6 is a flow chart showing an example of the inventive method of producing a solar cell; Figure 7 is a top view showing the electrode formation steps of the inventive solar cell; Fig. 8 is a schematic top view showing an example of the inventive solar cell;

Figure 9 is a top schematic view showing an example of the solar cell investigated by the present inventors;

Fig. 10 is a schematic cross sectional view showing an enlarged portion of the solar cell investigated by the present inventors;

Figure 11 is a schematic cross-sectional view showing an enlarged portion of the solar cell investigated by the present inventors;

Fig. 12 is a top view showing the electrode formation steps of the solar cell investigated by the present inventors;

Figure 13 is a schematic top view of a rear side showing an example of a fault generated in the solar cell investigated by the present inventors;

Fig. 14 is a schematic cross-sectional view showing an anterior posterior surface electrode type solar cell;

Fig. 15 is a top view schematically showing the appearance of the rear side of an anterior posterior surface type electrode solar cell;

Figure 16 is a top view showing the electrode formation steps of the solar cell investigated by the present inventors;

Fig. 17 is a top view schematically showing the appearance of the rear side of a rear surface type electrode solar anterior cell disclosed in patent document 1;

Fig. 18 is an enlarged view showing an enlarged portion of the inventive solar cell, relative to which the solar cell shown in Fig. 2 is modified relative to the shape of the current collector;

Fig. 19 is an enlarged view showing an enlarged portion of the inventive solar cell, relative to which the solar cell shown in Fig. 2 is modified relative to the shape of the current collector;

Fig. 20 is a top schematic view showing an example of the inventive solar cell, with respect to which the solar cell shown in Fig. 8 is modified in relation to the shape of the current collector; and

Fig. 21 is a schematic top view showing an example of the inventive solar cell, with respect to which the solar cell shown in Fig. 8 is modified in relation to the shape of the current collector.

Description of realizations

As described above, there has been a demand to provide a solar cell with a wide passivation region, low wiring resistance, high parallel resistance and high conversion efficiency. There has also been a demand to provide a method of producing a solar cell that can produce a solar cell with a wide passivation region, low wiring resistance, high parallel resistance and high conversion efficiency at low cost.

The inventors have investigated to obtain a solar cell that satisfies such demands. First, we investigated a solar cell equipped with connecting rod electrodes arranged more inside than the previous ones, an insulating film (s) arranged (s) so as not to connect the finger electrodes and the connecting rod electrodes for different types of conductivity, and finger electrodes composed of contact parts and current collectors that form a three-dimensional structure with connecting rod electrodes. An example of such a solar cell is shown in Figures 9 to 11. Figure 9 is a schematic top view showing an example of the solar cell investigated by the present inventors. Figures 10 and 11 are schematic cross-sectional views each showing an enlarged portion of the solar cell investigated by the present inventors. On the other hand, Figure 10 is a schematic cross-sectional view taken along line 11 'of the solar cell shown in Figure 9. Figure 11 is a schematic cross-sectional view taken along the line 2-2 'of the solar cell shown in figure 9.

In the solar cell 110 shown in Figure 9, the wiring resistance is reduced by providing several first tie bar electrodes 137 and second tie bar electrodes 138, along with shortening the length of the finger electrodes as much as may be possible. In this solar cell, insulating films 124 and 125 are provided only in regions where finger electrodes and connecting rod electrodes for different types of conductivity intersect each other (hereinafter referred to as the insulating region) in order to provide various connecting rod electrodes. This makes the three-dimensional structure easily formed. In this solar cell, the shapes of the first contact part 126 and the second contact part 127 can be dot shapes, etc. except just below the insulating films, and you can decrease the contact area that way.

As shown in Figures 10 and 11, the first contact part 126 joins the region 120 of the first type of conductivity formed on the back side of the semiconductor substrate 113 having the first type of conductivity, and the first collector is formed current 135 thereon as shown in FIG. 9. Furthermore, the second contact part 127 joins the region 121 of the second type of conductivity, and the second current collector 136 is formed thereon as shown in Figure 9. The first current collector 135 is in electrical contact with the first connecting rod electrode 137, and the second current collector 136 is in electrical contact with the second connecting rod electrode 138. The other structures they are basically the same as in the solar cell shown in figure 14. On the light receiving surface side, the rough shape 114, the FSF layer 115 and the anti-reflective film 116 are arranged; and on the rear side, the first rear-side passivation film 119 and the second rear-side passivation film 118 are arranged.

Hereinafter, the method of producing a solar cell in which the connecting rod electrodes and the finger electrodes form a three-dimensional structure will be described with reference to Figures 12 and 16. Each of the Figures 12 and 16 is a top view showing the electrode formation steps of the solar cell investigated by the present inventors.

In the method shown in Figure 16, the contact electrodes 128 are discontinuously each formed into a dot shape (Figure 16 (1)), other wiring electrodes 129 are formed to connect these electrodes (Figure 16 (2) ), insulating films 125 'are provided only in the insulating regions (figure 16 (3)), and connecting rod electrodes 130 (figure 16 (4)). This case requires the step of forming the wiring electrodes 129 as described above, which increases the steps to increase the cost.

In the method shown in figure 12, first contact parts 126 and second contact parts 127 are formed (figure 12 (1)), insulating films 124 and 125 are formed only in the regions of isolation (figure 12 (2)) , and subsequently, second current collectors 136 and first current collectors 135 can be formed simultaneously with the formation of the first connection rod electrodes 137 and the second connection rod electrodes 138 (Figure 12 (3)). This can increase the cross section of the finger electrode without increasing the number of stages compared to the method shown in Figure 16, and thereby can decrease the wiring resistance.

In the solar cell shown in Figure 9, the insulating films 124 and 125 are partially formed only in the insulating regions. As a result, parts having the insulating films formed thereon and parts without the insulating film are contained at the point where tie rod electrodes will be formed. In this case, the connecting rod electrodes have a large area to be in contact with the substrate directly, and are susceptible to shunting. Furthermore, the insulating film generally has a thickness of 1 to 60 | im. Accordingly, when attempting to form the tie rod electrode on the insulating film, the amount of discharge becomes uneven to generate bleeding as shown in dashed parts in Figure 13. Herein, Figure 13 is a schematic top view of a rear side showing an example of a failure generated in the solar cell investigated by the present inventors. This causes a P-type finger electrode to be in contact with an N-type connecting rod electrode, for example, to decrease the parallel resistance of the solar cell, and thereby greatly decrease the conversion efficiency.

The present inventors have further investigated to resolve the aforementioned issue. As a result, it was found that the above issue can be solved by a solar cell provided with an insulating film (s) in the entire area just below the connecting rod electrodes in which the connecting rod electrodes connection and finger electrodes form a three-dimensional structure; thereby completing the inventive solar cell. It was also found that the aforementioned issue can be solved by a solar cell production method in which the connecting bar electrodes are formed only on the insulating film (s) and the connection and finger electrodes form a three-dimensional structure; thereby completing the inventive method of producing a solar cell.

Hereinafter, the inventive solar cell will be specifically described with reference to figures, but the present invention is not limited thereto. It should be noted that the following explanation mainly describes a case where the semiconductor substrate of a first type of conductivity is an N-type silicon substrate (i.e. the first type of conductivity is an N type, and the second type of conductivity is a type P). However, even when the semiconductor substrate of the first conductivity type is a P-type silicon substrate, the present invention can be similarly applied using a source of impurities such as boron, phosphorous, etc. inversely.

[Solar cell (back surface electrode type solar cell)]

Fig. 1 is a schematic top view showing an example of the inventive solar cell. Fig. 2 is an enlarged view showing an enlarged part of the inventive solar cell. Figures 3 to 5 are schematic cross-sectional views each showing an enlarged part of the inventive solar cell. On the other hand, Figure 3 is a cross-sectional view taken along line a-a 'of the solar cell shown in Figure 1; Figure 4 is a cross sectional view taken along line b-b 'of the solar cell shown in Figure 1; and Figure 5 is a cross sectional view taken along line c-c 'of the solar cell shown in Figure 1.

As shown in Figure 1, the inventive solar cell 10 is provided with the semiconductor substrate 13 of a first type of conductivity in which one of the main surfaces is a light receiving surface, the other main surface is a rear side. As shown in Figures 3 to 5, solar cell 10 is a solar cell in which the back side of this semiconductor substrate has region 20 of the first type of conductivity (N-type diffusion layer) and region 21 of a second type of conductivity (P-type diffusion layer), which has a type of conductivity opposite to the first type of conductivity, called a back surface electrode type solar cell.

As shown in Figures 2 to 5, the solar cell 10 is further provided with a first finger electrode (s) composed of the first contact part 26 attached to the region 20 of the first type of conductivity and the first current collector 35 formed on the first contact part 26. It is also provided with a second finger electrode (s) composed of the second contact part 27 joined to the region 21 of the second type of conductivity and the second current collector 36 formed on the second contact part 27. In addition, the first connection bar electrode 37 which is in electrical contact with the first current collector 35 was also provided; and the second connecting rod electrode 38 which is in electrical contact with the second current collector 36.

As described above, the first current collector 35 and the second current collector 36 are attached to the first contact part 26 and the second contact part 27 respectively, which can collect current from the contact parts to the bar electrodes of connection.

In this solar cell 10, as shown in Figures 3 to 5, it is possible to form a rough shape 14 and an FSF layer (N-type diffusion layer) 15 on the light receiving surface side of the semiconductor substrate 13 of a first type of conductivity. On the resistant form 14, it is possible to form an anti-reflective film 16 containing silicon nitride, etc. A dielectric passivation layer (not shown in the figures) can be formed between the FSF layer 15 and the anti-reflective film 16.

On the back side of the semiconductor substrate 13 of a first type of conductivity, an oxide layer may be formed (a first backside passivation film) 19. It is also possible to form a second backside passivation film 18 on the layer of Rust 19. It is preferable that each of the light receiving surface and the back side is covered with a protective layer (a passivation film). The passivation film is preferably composed of one or more materials selected from a silicon oxide film, a silicon nitride film, and an aluminum oxide film.

As shown in Figure 2, the solar cell 10 is provided with insulating films 24 and 25 at least in the complete area just below the first connecting rod electrode 37 and the second connecting rod electrode 38. On the insulating film 24, the first current collector 35 and the first connection bar electrode 37 are in electrical contact with each other. On the insulating film 25, the second current collector 36 and the second connection bar electrode 38 are in electrical contact with each other.

Each of the insulating films 24 and 25 is generally formed to a thickness that can cover the top and the side of the first contact part 26 and the second contact part 27 on the contact parts just below the first electrode of connection bar 37 and the second connection bar electrode 38.

In the solar cell 10, as shown in Figures 2 to 5, the first contact part 26 and the second contact part 27 are each in a continuous line shape at least just below the insulating films 24 and 25. As shown in figure 5, the connecting rod electrode and the finger electrode for different types of conductivity can be physically attached through the insulating films 24 and 25 in the solar cell 10. That is, a connecting rod electrode and a current collector for different types of conductivity are not electrically bonded (they are separate). On the other hand, in a region where the connecting rod electrode and the finger electrode for the same type of conductivity intersect each other (closest part), the insulating films 24 and 25 are sandwiched between the contact part and the collector current collector as shown in figure 5. That is, a bus bar electrode and a current collector for the same type of conductivity are electrically bonded onto an insulating film. On the other hand, 37 (35) in figure 5 indicates a part where the first connection bar electrode 37 and the first current collector 35 (electrically connected) overlap.

In such a solar cell, it is possible to form a three-dimensional structure of the connecting rod electrode (s) and the finger electrode (s) by installing the insulating film (s) . This makes it possible to increase the number of connecting rod electrodes and shorten the length of the finger electrodes. Since the connecting rod electrode will not be in contact with the silicon substrate, the solar cell does not generate shunt. By forming the insulating film (s) in the entire area just below the connecting rod electrodes, it is possible to insulate the finger electrode (s) from the second (s) connection rod electrode (s) more securely, and isolate the second finger electrode (s) from the connection rod electrode (s) more safely without generating fault process in the formation of the connecting rod electrodes. This can provide a solar cell with high parallel resistance and high conversion efficiency. In the inventive solar cell, the contact part attached directly to the substrate itself is formed in a continuous line shape just below the insulating film. Accordingly, it is possible to reduce a step to connect the contact parts to each other as shown in Fig. 16 (2), and to produce a low cost solar cell in high performance.

Hereinafter, each component of the inventive solar cell will be described more specifically.

[First conductivity type semiconductor substrate]

The semiconductor substrate that can be used in the present invention is not particularly limited. For example, a N-type silicon substrate can be used. In this case, the thickness of the substrate can be a thickness of 100 to 200 | im, for example. The shape and area of the main surface of the substrate are not particularly limited.

[Contact part]

As the material for the first contact part and the second contact part, it is possible to use a fluid paste in which silver powder and glass frit are mixed with an organic binder (hereinafter referred to as sintered paste) , for example.

As described above, the contact part directly attached to the substrate itself must be formed in a continuous line shape just below the insulating film, but on the other side, the shape of the contact part is not particularly limited. For example, it is preferable that the contact part has a dot shape, a line shape, or a combination thereof in a part where the insulating film does not form. For example, if the shape of the contact part on the part is in the form of a point, the contact area may be made smaller. This makes it possible to widen the passivation region and thereby increase the open circuit voltage.

It is also preferable that the width and length of the insulating film formed just below the connecting rod electrode be greater than that of the connecting rod electrode. This design makes it possible to sufficiently separate the first connection bar electrode and the second contact part, and sufficiently separate the second connection bar electrode and the first contact part. Such a design also allows the insulating film to sufficiently cover the flank of the contact part. Therefore, it is possible to safely achieve the isolation between electrodes for different types of conductivity.

[Insulating film]

The insulating film forms at least in the entire area just below the connecting rod electrodes. The number and shape of the insulating film are not particularly limited. As shown in Figure 1, the insulating film is preferably in a continuous line form. As another example of the shape of the insulating film, there may be mentioned the shape shown in Figure 8. Herein, Figure 8 is a top schematic view showing an example of the inventive solar cell. Fig. 8 shows an embodiment in which the insulating film 25 'is largely formed, and the insulating film 24 (the insulating film just below the first tie bar electrode 37) and the insulating film 25 are integrated and formed. (the insulating film just below the second connecting rod electrode 38) in Fig. 1. Provided that a part of the insulating film 25 'is opened as shown in Fig. 8 in order to make the structure Electrode is a three-dimensional structure and carry the connecting rod electrode and finger electrode so that the same type of conductivity is in contact with each other. When the insulating film is in a shape shown in Figure 8, the contact part (s) and the other part (s) are the same height, and therefore displacement in the next step of forming a current collector (s) by printing. The insulating film shown in Figure 1 and Figure 8 prevents the tie rod electrode from directly contacting the substrate, and reduces roughness in a region where the tie rod electrode is formed to prevent shunting due to generation of bleeding in the formation of the connecting rod electrode.

It should be noted that the insulating film is generally formed to cover the side part and the top part of the contact part just below the connecting rod electrodes. The insulating film preferably has a width and length greater than that of the connecting rod electrode.

The thickness of the insulating film is preferably from 1 to 60 | im, more preferably from 5 to 40 | im, and particularly preferably from 10 to 30 | im. Such a thickness makes it possible to further improve the insulation property. It does not form excess insulating film, and therefore it is possible to produce a desirable solar cell at a lower cost.

This insulating film is preferably composed of a material (hereinafter, described as an insulating material) that contains at least one or more resins selected from the group consisting of silicone resins, polyimide resins, polyamide-imide resins , fluororesins, phenolic resins, melamine resins, urea resins, polyurethanes, epoxy resins, acrylic resins, polyester resins and poval resins. Particularly, when a heat treatment is carried out on the formation of the current collector and the connecting rod electrode, it is desirable to select a heat resistant resin. For example, the siloxane bond, which is a backbone of a silicone resin, has high binding energy and is stable, thereby having superior heat and weather resistance compared to organic polymeric materials with a backbone. composed of a main carbon structure. Other resins become materials with high heat resistance by introducing an aromatic ring into the molecular chain.

[Current collector, connecting rod electrode]

The current collector and the connecting rod electrode are preferably composed of a material containing one or more kinds of conductive materials selected from the group consisting of Ag, Cu, Au, Al, Zn, In, Sn, Bi and Pb, and one or more classes of resins selected from the group consisting of epoxy resins, acrylic resins, polyester resins, phenolic resins, and silicone resins. These parts composed of such an electrode material do not have to contain glass frit, and consequently the electrode material is not directly bonded to the semiconductor substrate as a heating silicon substrate, and the increased area can be suppressed contact.

The number of the connecting rod electrode is not particularly limited, but it is preferable that the total number be 4 or more and 10 or less. This makes it possible to decrease the wiring resistance of the finger electrode, and improve conversion efficiency. On the other hand, the shape of the connecting rod electrode is not particularly limited. For example, the shape of the connecting rod electrode may be a discontinuous shape divided in the longitudinal direction of the connecting rod electrode. As the shape of the connecting rod electrode, the continuous line shape is preferable. Such a form can be easily produced.

As shown in figure 1, etc., the current collector and the connecting rod electrode can be formed to intersect at right angles.

On the other hand, the first finger electrode is generally formed in a direction along the longitudinal direction of the region of the first type of conductivity. The second finger electrode is generally formed in a direction along the longitudinal direction of the region of the second type of conductivity. In general, finger electrodes are formed in the plural number.

[Method to produce solar cells]

Fig. 6 is a flowchart showing an example of the inventive method for producing a solar cell. Hereinafter, an example of the inventive method for producing a back surface electrode type solar cell will be described with reference to the schematic cross-sectional views shown in Figures 6 (a) to (1). Particularly, it is exemplified in one case of a type N silicon substrate. Hereinafter, the region of the first type of conductivity is also described as an N-type diffusion layer, and the region of the second type of conductivity is also described It is described as a P-type diffusion layer. The method described below is a typical example, and the present invention is not limited thereto.

First, the N 13 type silicon substrate with a thickness of 100 to 200 | im is prepared, for example, as a semiconductor substrate of the first type of conductivity in which one of the main surfaces becomes a reception surface of light, and the other main surface becomes a back side. One of the main surfaces of this N 13 type silicon substrate becomes a light receiving surface, and the other main surface becomes a back side. Then, as shown in Figure 6 (a), a texture mask 31 is formed as a silicon nitride film on a back side (hereinafter referred to as "back side of an N-type silicon substrate "), Which is a back side of a face to be a light receiving surface of this N type silicon substrate 13 (hereinafter referred to as" light receiving surface of a N type silicon substrate) ”) By a CVD method or a cold discharge metallization method, etc.

Subsequently, a rough shape 14, which is a textured structure, is formed on the light receiving surface of the N-type silicon substrate 13 by etching as shown in Figure 6 (b). Chemical etching is done, for example, by using a solution in which isopropyl alcohol is added to an aqueous alkaline solution including sodium hydroxide or potassium hydroxide and heated to 60 ° C or higher and 80 ° C or less.

The next stage will then be described by using Figure 6 (c). After removing the texture mask 31 formed on the back side of N-type silicon substrate 13, diffusion masks 32 and 33 are formed as silicon oxide films on the light receiving surface and the back side of the silicon substrate type N 13 as shown in figure 6 (c). To a part where the N-type diffusion layer will be formed, the chemical etching paste is applied by a screen printing method, etc., and it undergoes heat treatment to remove the diffusion mask 32 in the part where it will form. the N-type diffusion layer to expose the substrate. The etching paste after the pattern making treatment is subjected to ultrasonic cleaning and removed by acid treatment. This etching paste contains at least one etching component selected from the group consisting of phosphoric acid, hydrogen fluoride, ammonium fluoride, and ammonium hydrogen fluoride, and contains water, an organic solvent, and a thickener, for example. This treatment can be done using a photolithography method.

After this, to the exposed part on the back side of the N 13 type silicon substrate, phosphorus as N type impurity is diffused by vapor phase diffusion using PoCl3 to form a N 20 type diffusion layer. The type diffusion layer N can be formed by centrifugal coating of a solution, in which the N-type impurity, such as phosphoric acid, is dissolved in alcohol or water, and the performance of thermal diffusion.

Subsequently, as shown in Figure 6 (d), treatment with hydrofluoric acid is performed to remove the diffusion mask 32 and diffusion mask 33 formed on the N 13 type silicon substrate, as well as glass layers formed by diffusion of phosphor inside the diffusion masks 32 and 33, and then thermal oxidation is carried out on a oxygen or vapor atmosphere to form a silicon oxide film 34.

Then, as shown in Figure 6 (e), to a part where a P-type diffusion layer will form on the back side of the N-13 silicon substrate, the etch paste is applied by a screen printing method , etc., and this is heat treated to remove the diffusion mask 34 in the part where the P-type diffusion layer will be formed to expose the substrate. The etching paste after the pattern making treatment is subjected to ultrasonic cleaning and removed by acid treatment. This etching paste contains at least one etching component selected from the group consisting of phosphoric acid, hydrogen fluoride, ammonium fluoride, and ammonium hydrogen fluoride, and contains water, an organic solvent, and a thickener, for example.

As shown in Figure 6 (f), the back side of the N 13 type silicon substrate is coated by centrifugation with a solution in which a source of P type impurity, such as boric acid, is dissolved in alcohol or water, and after drying, the exposed part on the back side of the N 13 type silicon substrate is subjected to heat treatment to diffuse boron as a P-type impurity inside, thus forming a P-21 diffusion layer. In this case, the P 21 type diffusion layer may also be formed by a vapor phase diffusion method using BBr3, etc.

The next stage is then described using Figure 6 (g). As shown in Figure 6 (g), hydrofluoric acid treatment is performed to remove the silicon oxide film 34 formed on the N 13 type silicon substrate, and a glass layer formed by boron diffusion on the film of silicon oxide 34. Accordingly, on the back side of the N-type silicon substrate 13, a first backside passivation film 19 is formed which doubles as a diffusion mask as a silicon oxide film by a CVD method or applying SOG (centrifugation on glass) and baking.

Subsequently, as shown in Figure 6 (h), on the light receiving surface of the N 13 type silicon substrate, an n layer (FSF layer 15) can be formed, which is a receiving surface diffusion layer light, by a centrifugal coating method of a solution in which N-type impurities such as phosphoric acid are dissolved in alcohol or water followed by thermal diffusion, or by a vapor diffusion method using PoCl3.

On the back side of the N 13 type silicon substrate, a second back side passivation film 18, such as a nitride film, is formed by CVD or a spray method as shown in Figure 6 (i). The nitride film can also be formed on the front face as CVD anti-reflective film 16 or a spray method.

In the present invention, the method of forming region 20 of the first type of conductivity (N-type diffusion layer) and region 21 of the second type of conductivity (P-type diffusion layer) on the back side of the N-type silicon substrate It is not limited to the method shown in Figure 6 (a) to (i), and can be appropriately altered.

Then, as shown in Figure 6 (j), electrodes are formed on the N-type diffusion layer 20 and the P-21 type diffusion layer formed on the back side of the N-type 13 silicon substrate.

Fig. 7 is a top view showing the electrode formation steps of the inventive solar cell. As shown in Figure 7, the first contact part 26 and the second contact part 27 are electrodes for contacting the silicon substrate. Each electrode pattern of these contact parts must be a continuous line pattern in at least one region where the contact part and the connecting rod electrode intersect. Elsewhere, it can be a discontinuous shape, such as ellipses, rectangles, and points, or it can be a line shape. These forms can coexist in them. By forming the line-shaped contact part in the region where the contact part and the connecting rod electrode intersect, it is possible to collect current generated over the region 21 of the second type of conductivity just below the first connecting rod electrode 37, for example, although the contact part has any shape in other regions.

It is desirable that the ratio of each area of the first contact part and the second contact part based on the surface of the substrate is approximately 1% to 6%. For example, when the distance between the finger electrodes is 1.5 mm pitch, the line width will be from 14 | im to 90 | im. This is because a back surface electrode (a contact part) with a smaller contact area can increase the passivation region, allowing the open circuit voltage to increase.

This contact part can be formed by screen printing, for example, using a build plate that has an opening with a line-shaped pattern and so on as described above. It can be formed by other procedures using transfer printing, inkjet printing, a dispenser, a deposition method, etc.

A specific method of forming a contact part, etc. will be described with reference to Fig. 6 (j) and Fig. 7. First, the sintering paste is formed on the N 20 type diffusion layer or the P 21 type diffusion layer by the aforementioned printing method using the sintering paste mentioned above as raw material for the contact parts. Then, the first contact part 26 or the second contact part 27 can be formed by baking this sintering paste at a temperature of 700 to 800 ° C for 5 to 30 minutes. At this stage, each of the first contact part 26 attached to region 20 of the first conductivity type and the second contact portion 27 attached to region 21 of the second conductivity type is formed to have a continuous line shape to the minus a part of it (figure 7 (1)). As will be described later, in this part having a continuous line shape, the contact part and the connecting rod electrode intersect each other.

Such use of the glass frit-containing sintering paste allows the glass frit to melt in the oven simultaneously with the melting of the second rear-side passivation film 18 and the first rear-side passivation film 19, and by Consequently, the electrodes adhere to the substrate itself in order to directly bond to the substrate with the penetration of these films. It should be noted that an n + electrode and a p + electrode (the first contact part, the second contact part) can be printed simultaneously and baked simultaneously. Printing and baking can also be performed in succession.

Then, the formation of the insulating film will be described. Figure 6 (k) is a cross-sectional view of a P-type connecting bar electrode, and Figure 6 (l) is a cross-sectional view of an N-type connecting bar electrode (a first bar electrode of connection). These show a cross-sectional view taken along line a-a 'and a cross-sectional view taken along line b-b' of the solar cell shown in Figure 1, respectively.

Insulating films 24 and 25 are formed to cover the top and the side of the part having a continuous line shape at the first contact part 26 and the second contact part 27 (Figure 7 (2)).

As the material for the insulating film, it is possible to use the above-mentioned resin-containing material such as a silicone resin (insulating material). To form this material on a solar cell substrate, it is recommended to use paste material in which solvent is added to give fluidity (insulating paste). When fluent, transfer printing, screen printing, a dispenser, etc. can be used.

For example, to form a pattern of insulating films as shown in Figure 7, it is possible to use a printing plate that has an opening in the same shape as this pattern. Using this printing plate, the insulating films can be screen printed to apply the insulating paste in a prescribed position on the N 13 type silicon substrate, and by heat treating at 350 ° C or below for 5 to 30 minutes to cure the insulating paste (figure 7 (2)). The insulating films can also be formed at desired positions by a method in which the insulating film is formed over the entire surface and then subjected to etching and embossing treatment using photolithography.

Then, a method for forming the first connecting rod electrode and the second connecting rod electrode will be described. As described above, the production method shown in Figure 12 can bring the connecting rod electrode into contact with the substrate directly for shunting, and can cause bleeding to form in the connecting rod electrode (Figure 13). ) due to the roughness of the substrate surface caused by the partial formation of the insulating film, thereby causing the electrodes for different types of conductivity to be connected to each other by the connecting rod electrode protruding from the insulating film. These failures reduce the parallel resistance of the solar cell to decrease the conversion efficiency.

Accordingly, in this stage of the present invention, the first connecting rod electrode 37 and the second connecting rod electrode 38 are formed only on the insulating films 24 and 25. Particularly, when the connecting rod electrode is formed in a rectangle in a continuous body as shown in figure 7, the insulating film is formed in a rectangle in a continuous body. That is, the insulating film is formed just below the connecting rod electrode. This decreases the roughness in the region where the connecting rod electrode will form. The present invention has a structure in which the connecting rod electrode is not in contact with the N 13 type silicon substrate and the contact part directly, and the insulating film is inserted between them. When the insulating film has a small area, the insulating film and the connecting rod electrode have the same shape. In the present invention, it is preferable that the width and length of the insulating film be greater than that of the connecting rod electrode. This makes it possible to separate the connecting rod electrode and the substrate more safely. This also decreases the roughness in the region where the connecting rod electrode will be formed, and consequently it is possible to suppress bleeding in the formation of the connecting rod electrode. When forming the connecting rod electrode by screen printing, it is desirable to arrange the printing direction so that it is nearly parallel to the longitudinal direction of the connecting rod electrode to minimize bleeding in the width direction.

Subsequently, the method for forming the first current collector and the second current collector will be described.

In this stage of the present invention, the first current collector 35 that is in electrical contact with the first connecting rod electrode 37 is formed on the first contact part 26, and the second current collector 36 that is in electrical contact with the second connecting rod electrode 38 it is formed on the second contact part 27 (figure 7 (3)).

In this phase, it is preferable that the stage for forming the first connection bar electrode and the second connection bar electrode and the stage for forming the first current collector and the second current collector are performed simultaneously. This makes it possible to further reduce the number of stages, and produce a solar cell with high conversion efficiency at a lower cost.

When the current collector is formed using a printing method such as screen printing, the shape (pattern) of the current collector is preferably such as the shapes shown in Figures 18 to 21. In Figures 18 to 21, it is intended print the current collector from right to left. In general, the prints can be marked at the print end (eg, the parts with dashed lines in Figure 2 and Figure 8). In this case, if the current collector has such shapes as shown in Figures 18 to 21, the print end of the current collector only exists on the insulating film without existing on the contact part. Accordingly, these shapes make it possible to prevent the print to form a current collector from being marked on the contact part, and to prevent the line width of the current collector from extending from the line width of the contact part. As a result, it is possible to easily produce a solar cell that is difficult to drift. On the other hand, Figures 18 and 19 are enlarged views showing an enlarged part of the inventive solar cell, with respect to which the solar cell shown in Figure 2 is modified with respect to the shape of the current collector. Figures 20 and 21 are a top schematic view showing an example of the inventive solar cell, with respect to which the solar cell shown in Figure 8 is modified in relation to the shape of the current collector.

In this case, the upper part of the connecting rod electrode is welded with Pb-Sn coated Cu wiring and so on called flange wiring, and then the solar cell is encapsulated between glass and encapsulant to be a module with the In order to maintain power even when subjected to outdoor exposure. Accordingly, the connecting rod electrode can be continuous or discontinuous as long as it has adhesiveness to the flange wiring.

As the material for forming the current collector and the connecting rod electrode, it is desirable to use the above mentioned thermosetting paste which contains one or more kinds of conductive materials selected from the group consisting of Ag, Cu, Au, Al, Zn, In , Sn, Bi, and Pb, and one or more classes of resins selected from the group consisting of epoxy resins, acrylic resins, polyester resins, phenolic resins, and silicone resins. Because such a thermosetting paste makes it possible to carry out a heat treatment to form the electrode at a temperature of less than 400 ° C, which does not decompose the insulating material, which contains organic material suitable for the material of the insulating film.

For example, the thermosetting paste having solvent added thereto is applied to a prescribed position by screen printing, and then dried, heated at 350 ° C or below for 5 to 30 minutes to cure. In this method, the thermosetting paste does not contain glass frit unlike the sintering paste of the raw material of the contact part. Consequently, the electrode material (the thermosetting paste) does not directly bond to the silicon substrate on heating, and the increase in contact area is suppressed. It is also possible to use such a thermosetting resin paste to bond the flange wiring and the connecting rod part followed by heat treatment. This makes it possible to adhere the flange wiring and the connecting rod part without soldering.

Examples

Hereinafter, the present invention will be described in more detail with reference to the example and comparative example, but the present invention is not limited to this example.

(Example and comparative example)

In order to confirm the validity of the present invention, the following steps were performed on 100 pieces of semiconductor substrates (50 pieces each of Example 1 and Comparative Example 1) to produce 100 pieces of solar cells. Each of these was fitted with three pairs of connecting rod electrodes.

As shown in Figure 6, first, on the back side of a 15 cm square N 13 type silicon substrate with a thickness of 200 | im, a 200 nm silicon nitride film was formed by a CVD method to be a texture mask 31 (figure 6 (a)). Subsequently, on the light-receiving surface of the N-type silicon substrate 13, a textured structure (a rough shape) 14 was formed with a solution in which isopropyl alcohol had been added to the aqueous solution of potassium hydroxide (figure 6 b)).

Subsequently, the texture mask 31 formed on the back side of the N-type silicon substrate 13 was removed with hydrofluoric acid solution, and then silicon oxide films were formed on the light receiving surface and the back side of the substrate. silicon type N 13 as diffusion masks 32 and 33 by thermal oxidation. TO the parts that are going to form an N-type diffusion layer, chemical etching paste composed mainly of phosphoric acid was applied by screen printing. Diffusion mask 32 was removed in part to form an N-type diffusion layer by heat treatment to expose the substrate (Figure 6 (c)). The etching paste after the stamping treatment was subjected to ultrasonic cleaning and removed by acid treatment. Following this, to the exposed part on the back side of the N 13 type silicon substrate, the phosphorus was diffused as N type impurity by vapor phase diffusion using PoCl3 to form a N 20 type diffusion layer (Figure 6 (c )).

Subsequently, the treatment with hydrofluoric acid was performed to remove the diffusion mask 32 and the diffusion mask 33 formed on the silicon substrate type N 13, as well as glass layers formed by diffusion of phosphorus in the diffusion masks 32 and 33 , and then thermal oxidation with oxygen was performed to form a silicon oxide film 34 (Figure 6 (d)). Then, the silicon oxide film 34 was removed in one part to form a P 21 type diffusion layer on the back side by etching (Figure 6 (e)).

The back side of the N 13 type silicon substrate was centrifuged coated with an aqueous solution containing boric acid, and after drying, heat treated to diffuse boron as a P-type impurity on the exposed part on the back side of the substrate of N 13 type silicon, thereby forming a P 21 type diffusion layer (Figure 6 (f)).

Subsequently, as steps corresponding to Figures 6 (g) to (i), the treatment with hydrofluoric acid was performed to remove the silicon oxide film 34 formed on the N 13 type silicon substrate, and a glass layer formed by Boron diffusion into the silicon oxide film 34, and then silicon nitride films were formed on the front surface and the back side as passivation films by a CVD method. The procedures for this step were performed in each of Example 1 and Comparative Example 1 as common steps. Subsequently, electrode formation was performed.

[Example 1]

In Example 1, contact parts, insulating films, current collectors, and connection bar electrodes were formed in a pattern shown in Figures 2 and 7 (Figures 6 (j) through (1)).

First, the contact parts were formed into a pattern of line shapes, each having a width of 100 | im. Specifically, conductive paste (sintering paste) composed of Ag particles, glass frit, binder and solvent was applied to prescribed parts on the diffusion layer by screen printing. This was dried and baked at 700 ° C for 5 minutes to form first contact parts 26 and second contact parts 27. Insulating films were then formed each having a width of 3 mm (in the longitudinal direction of the electrode of finger) and a length of 150 mm (in the longitudinal direction of the connecting rod electrode) just below the connecting rod electrodes to intersect the finger electrodes (contact parts) at right angles. As the raw material for the insulating films, polyimide paste was used. This paste was applied to the prescribed parts by screen printing, and heated at 150 ° C for 20 minutes for curing, thereby forming insulating films.

Then, current collectors each having a width of 100 [mu] im and connecting rod electrodes each having a width of 1.2 mm and a length of 148 mm were simultaneously formed. As raw material for current collectors and connecting rod electrodes, conductive paste (thermosetting paste) composed of Ag particles and thermosetting resin was used. This thermosetting paste was silk-screened, dried and heated at 200 ° C for 30 minutes to cure, thereby forming the first current collectors 35, the second current collectors 36, the first connection rod electrodes 37 and the second connecting rod electrodes 38 simultaneously.

[Comparative Example 1]

In Comparative Example 1, contact parts, insulating films, current collectors, and connection bar electrodes were formed in a pattern shown in Figures 9 and 12.

First, contact parts were formed into a line shape pattern each having a width of 100 | im. Specifically, conductive paste (sintering paste) composed of Ag particles, glass frit, binder and solvent was applied to prescribed parts on the diffusion layer by screen printing. This was dried and baked at 700 ° C for 5 minutes to form first contact parts 126 and second contact parts 127. Insulating films were then formed each having a length of 3 mm (in the longitudinal direction of the electrode of finger) and a width of 500 | im (in the longitudinal direction of the connecting rod electrode) only for isolation regions (the region where the finger electrode and connecting rod electrode for different types of conductivity intersect each other) . As the raw material for the insulating films, polyimide paste was used. This paste was applied to the prescribed parts by screen printing, and heated at 150 ° C for 20 minutes to cure, thereby forming insulating films.

Then, current collectors each having a width of 100 and connecting rod electrodes each having a width of 1.2 mm and a length of 148 mm were simultaneously formed. As raw material for the current collectors and for the connection bar electrodes, conductive paste (thermosetting paste) composed of Ag particles and thermosetting resin was used. This thermosetting paste was silk-screened, dried and heated at 200 ° C for 30 minutes to cure, thereby forming the first current collectors 135, the second current collectors 136, the first connection bar electrodes 137 and the second connecting rod electrodes 138 simultaneously.

The 100 pieces of solar cells thus produced were evaluated using a solar simulator (in an atmosphere of 25 ° C, light intensity 1 kW / m2, global AM1.5 spectrum). The parallel resistance of each solar cell was also measured. The results are shown in Table 1. Table 1 shows the proportions of the substrates with the parallel resistance that is more than 1000 Qcm2. The conversion efficiency in Table 1 shows each average of 50 pieces of solar cells from Example 1 and Comparative Example 1.

[Table 1]

Table 1 is a table showing the experimental results of Example 1 and Comparative Example 1. As shown in Table 1, Comparative Example 1 gave solar cells having a parallel resistance of 1000 Qcm2 or less in high proportion, and the conversion efficiency was greatly reduced. On the other hand, Example 1 gave solar cells with a sufficiently high parallel resistance and high conversion efficiency. This is because the insulating films were formed in the entire area just below the connecting rod electrodes, and the connecting rod electrodes were not in direct contact with the substrate in this way. This is also due to the flatness of the surfaces of the insulating films (regions where the connecting rod electrodes were formed), which could suppress bleeding in the formation of the connecting rod electrodes, and therefore the former finger electrodes and the second finger electrodes were not in contact with the second connecting rod electrodes and the first connecting rod electrodes respectively.

It should be noted that the present invention is not limited to the aforementioned embodiment. The embodiment is only an exemplification, and any examples having substantially the same characteristics and demonstrating the same functions and effects as those of the technical concept described in the claims of the present invention are included in the technical scope of the present invention.

Claims (8)

1. Solar cell (110) comprising: a semiconductor substrate (113) of a first type of conductivity in which one of the main surfaces is a light receiving surface, the other main surface is a back side, and the back side of the semiconductor substrate has a region of the first type of conductivity and a region of a second type of conductivity, a type of conductivity being opposite to the first type of conductivity; a first finger electrode including: a first contact part (126) attached to the region (120) of the first type of conductivity; and a first current collector (135), at least a part of the first current collector being formed in the first contact part; a second finger electrode including: a second contact part (127) attached to the region (121) of the second type of conductivity; and a second current collector (136), at least a part of the second current collector being formed in the second contact part; a first connecting rod electrode (137) being in electrical contact with the first current collector; a second connecting rod electrode (138) being in electrical contact with the second current collector; and an insulating film (124, 125) disposed at least in the complete area just below the first connection rod electrode and the second connection rod electrode; where the electrical contact between the first current collector (135) and the first connection bar electrode (137), as well as the electrical contact between the second current collector (136) and the second connection bar electrode (138) they are made on the insulating film; and the first contact part (126) and the second contact part (127) are each in a continuous line shape at least just below the insulating film. 2. Solar cell according to claim 1, wherein the first connecting rod electrode and the second connecting rod electrode are each in a continuous line form, and the insulating film is in a continuous line form. 3. Solar cell according to claim 1 or 2, in which the total number of the first connecting rod electrode and the second connecting rod electrode is 4 or more and 10 or less. Solar cell according to any of claims 1 to 3, in which the insulating film is composed of a material containing one or more resins selected from the group consisting of silicone resins, polyimide resins, polyamide-imide resins, fluororesins, phenolic resins, melamine resins, urea resins, polyurethanes, epoxy resins, acrylic resins, polyester resins and poval resins. 5. Solar cell according to any of claims 1 to 4, wherein the insulating film has a thickness of 1 to 60 | im. Solar cell according to any one of claims 1 to 5, wherein the first current collector, the second current collector, the first connection rod electrode and the second connection rod electrode are each composed of a material containing one or more classes of conductive materials selected from the group consisting of Ag, Cu, Au, Al, Zn, In, Sn, Bi and Pb, and one or more classes of resins selected from the group consisting of epoxy resins, resins acrylics, polyester resins, phenolic resins and silicone resins. 7. A method of producing a solar cell that includes a semiconductor substrate of a first type of conductivity in which one of the main surfaces of the semiconductor substrate is a light receiving surface, the other main surface is a back side, and the rear side of the semiconductor substrate has a region of the first type of conductivity and a region of a second type of conductivity, a type of conductivity being opposite to the first type of conductivity; which includes the stages of: forming the region of the first type of conductivity and the region of the second type of conductivity on the back side; forming a first contact part attached to the region of the first type of conductivity and a second contact part attached to the region of the second type of conductivity so that each of them has a continuous line shape in at least part of it; forming an insulating film to cover the top and the side of the part having a continuous line shape at the first contact part and the second contact part; forming a first connection bar electrode and a second connection bar electrode only on the insulating film; forming a first current collector that is in electrical contact with the first connecting rod electrode in the first contact part; and forming a second current collector that is in electrical contact with the second connecting rod electrode on the second contact part. The method of producing a solar cell according to claim 7, wherein the step of forming a first connection bar electrode and a second connection bar electrode and the step of forming a first current collector and a second collector currents are made simultaneously.